Method of manufacturing relays



March 14, 1967 J. N. PEARSE 3,308,527

METHOD OF MANUFACTURING RELAYS Original Filed July 23 1962 2 SlleetS-Sheet l i l X Y INVENTOR JAMES N. PBARSE ATTORNEY March 14, 1967 J. N. PEARSE 3,308,527

METHOD OF MANUFACTURING RELAYS Original Filed July 25, 1962 2 Sheets-Sheet 2 w37 1oz MAGNET AM Pe E T Un Ns '26 2f;

\ 2 7 zooo l I l l 2500 Z000 |500 |000 500 FIELD NTENSITY IN OERSTEDS INVENTOR JAMES N. PEARSE ATTORNEY col'. FLUX IN AMPERE TURNS .f-(NEGATIVE CURRENT) o `1 T FLUX DENSITY 1N :Muss

3 Claims. (Cl. 29-155.5)

This is a division of an application Ser. No. 211,628, led July 23, 1962, now Patent No. 3,239,626.

The present invention relates to relays and components thereof, and particularly to relays incorporating sealed reed switching units and to a method of manufacturing said relays.

A principal object of the present invention is to provide an electromagnetic relay including a plurality of commiugled sealed reed switching units actuated by a common coil, and wherein the operating characteristics of one unit will in no manner interfere with the operating characteristics of adjacent or otherwise proximately disposed switching units, such units being selected from type having operating characteristics, such as normally-open, normally-closed, normally-closed contacts selectively responsive to or currents, latching contacts that latch with (-l-) or currents and unlatch with or currents, respectively, and paired latching contacts having one switching member latching on (-1-) and unlatching on current and the other member of the pair latching on and unlatching on current, and wherein only one biasing magnet is required for a respective pair of latching switches.

A corollary object of the present invention lies in the provision of sealed reed contacts disposed in the same relay coil in close proximity with one another, and wherein certain of said contacts are operated as magnetically biased, normally-closed contacts, and being so arranged as to not affect the operation of the normally-open or weakly biased latching switches disposed in the vicinity thereof.

It is a further object of the present invention to provide a relay construction utilizing sealed reed switching units wherein latching contacts may be provided in the same relay with normally-open and normally-closed contacts.

AIt is still another object o-f the present invention to provide means for adjusting the strength of a bias magnet used in conjunction with the normally-closed reed switching unit or with the latching switching units without altering the physical shape of the magnet or its proximity to the switch, thereby allowing means for compensating for variation in the reed switch operate characteristics and geometry within the relay coil to re-open at some bucking flux by the relay coil that is specified as a relay parameter.

It is a still further object of the present invention to provide a method of manufacturing an electro-magnetically operated relay utilizing sealed switching units, wherein the switching units are pre-selected for their individual operate and release characteristics and are thereafter arranged in a prescribed relationship to one another and to a magnetic coil to take advantage of the variations in intensity of flux induced by the coil and influencing the operation of the various switching units operated thereby, and wherein such pre-selection and arranging will further tend to permit the various switching units to operate or to release in unison.

The present invention disclosed herein nds application in relays of the type comprising a plurality of glasssealed reed contact devices arranged co-extensively in a group with a common coil surrounding thesame, which coil serves to simultaneously energize the reeds to conl United States Patent O M 3,308,527 Patented Mar. 14, 1967 ICC trol electrical circuits. A flux-carrying metallic casing substantially surrounds the coil as a means of directing the coil flux towards the reed switches. The reeds of such relays are also of known construction and are made of magnetic material of high electrical conductivity and may be plated with gold or other precious metal, if so desired. The contacts of each reed switch are preferably enclosed in a hermetically sealed, tubular envelope made of vitreous material such as glass. The envelope is filled with an inert gas such as helium, argon, neon or other non-corrosive gas and is sealed at each end to prevent escape of the gas and admission of foreign particles to the contact areas.

For a fuller understanding of the nature and objects of this invention, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which:

FIG. l is a view in longitudinal section taken in the plane of lines 1 1 0f FIG. 2 of a relay embodying the features ofthe present invention;

FIG. 2 is a cross-sectional View taken in the plane of lines 2-2 of FIG. l;

FIG. 3 is a top plan view of a biasing magnet used with certain of the switching units which may be used with the relay of the present invention;

FIG. 4 is a view in side elevation of the biasing magnet of FIG. 3, and indicating the ux path through an adjacent normally-closed or latched contact;

FIG. 5 is a diagrammatic view, partially in section of the apparatus in magnetizing the biasing magnet of FIG. 3;

FIG. 6 is a diagram of the demagnetization curves of ferrite material useful in manufacturing the biasing magnets of FIGS. 3 and 4;

FIG. 7 is a diagram of a typical set of curves illustrating the range of ampere-turns needed to operate and to release a typical group of normally-closed switches used in conjunction with the relay of this invention.

It is to be noted that in the views of FIGS. 1, 2 and 5 that various supporting members not forming a specific part of the present invention have been omitted for the sake of clarity in drawing and description. It will be obvious that additional supporting spacer members, terminals and other necessary appurtenances will be required in the commercial application of the relay of FIGS. l and 2. Stationary supporting members and other means of support are also required in the magnetizing apparatus of FIG. 5, but have also been eliminated for the sake of clarity and will be readily understood by those familiar with the art.

It has been observed that in the magnetic circuit of a relay coil there is considerable variation in the usable flux density affecting operation of the Various switching units actuated by the coil. That is, the magnetic field is known to be strongest at each of the corners of the lectangularly wound coil, and is somewhat lessened at leg portions intermediate these corners, whereas the magnetic eld affecting the operation of switching units disposed -centrally of a coil window is even .of relatively lesser intensity than that of the intermediate leg portions. It will be further :appreciated that nor-mal manufacturing procedures inevitably produce some variations in the switch operating characteristics. Tolerance limitations are difficult to maintain and changes in the unit cannot be made after sealing. This will lbe apparent from the following description of the Various switching units, designated generally by the reference numeral 10 (see FIGS. l and 2) and disposed in the window 11 of the coil 12. The switches 10 each comprise tw-o elongated metal strips or reeds 13 Iand 14 sealed in a glass tubular enclosure 15. The strips :are of ferromagnetic, electrically conducting metal, preferably of a nickel-iron alloy having a coefficient of expansion approxim-ately equal to that of the glass enclosure 15, land terminate in overlapping contact surfaces 16. The contact surfaces 16 may be coated with gold or other precious metal, if so desired. The interior 17 of the glass enclosure 15 is preferably filled with an inert gas to minimize contact contamination and deterioration through corrosion, etc. The space between the contacts 16 is quite minute and may be between 2 and 3 millimeters. Each metallic reed 13, 14 is anchored in the glass enclosure at 18. The switching units are manufactured as normally-open contacts, as shown in the units of the columns designated X and Y` of the View of FIG. 2. Application of a magnetic field from the coil 12 Causes the needs to assume 1a position parallel with the magnetic lines of force, thereby contacting each other.

A metallic-flux-car-rying casing 19 surrounds the coil 12. The casing 19 being of low reluctance, prevents the loss of ilux through other undesired paths and hence substantially all of the coil ilux is directed to, and concentrated at the gaps between the overlapped portions of the reeds 13 and 14.

It is often desirable, however, to provide normallyclosed contacts or biased closed latching contacts as shown in the switching unit 1t) of the columns designated by the reference character W of FIG. 2. Here a biasing magnet, indicated generally by the reference numeral 20, is provided to maintain the contacts in the normallyclosed position. In the case of latching contacts AW and BW (see FIG. 2), these contacts are normally open, as shown, but remain latched upon the iirst pulse of current of the Aproper direction in the coil 12, as will be later explained. The magnet 20 is provided with a keeper 21 of magnetic material. The magnet 2t)l and its manufacture form a part of the .present invention which will be hereinafter described.

It is also often desirable to provide paired latching contacts composed of adjacent switches, indicated as swtiching unit 10 of rows Y and Z of FIG. 2. In this case a magnet 22, without keeper is disposed between a pair of switching units 10, ias may be found in rows designated by the reference characters A, B, C, D of columns Y and Z of FIG. 2.

In the present embodiment, as aforementioned, there may be single and paired latching contacts. The action of the relay with respect to the latching contacts, in general, can be visualized by considering the directions of the magnetic elds produced by `the permanent magnets 20 or 22, respectively, in conjunction with the coil 12. An otherwise normally-open switch, su-ch as the switches AW and BW, is subject to the influence of an adja-cently disposed permanent magnet, but the force of `the magnet is maintained at a level not high enough to close the switch contacts. If, however, a pulse of current is sent through the coil 12, which sets up a flux in the same direction as the flux from the permanent magnet, the contacts will close. The permanent magnet then keeps t-hem closed with no further current required in the coil. To open Ithe contacts, ia second pulse of current is sent through the lcoil in the opposite direction and it produces a flux that opposes and overcomes the permanent magnet ux, thus releasing the reeds.

In the case of the paired latchingcontacts, such as those of columns Y and Z of FIG. 2, the switching units 10 are alternatively operated relative to one another, and are illustrated in a normal lor initial position with the contacts AY, BY, CY and DY open and the other respective pairs AZ, BZ, CZ and DZ in latched closed position. Thus, for instance, upon supplying the coil 12 wit-h a charge of current the contacts AZ, BZ, CZ and DZ will unlatch and their paired contacts AY, BY, CY and DY will latch closed. Reversal of supply current to current will return the contacts to the respective normal positions illustrated.

Having now outlined and described the various components which may be used to make up a relay, it will be apparent that heretofore a commingling of switching units has been next to impossible to provide in one coil, and only then where provision was made for considerable spacing .between each of the switching units to avoid the problem of having the operation of one unit affect the operation of a unit of differing magnetic characteristics. The present invention contemplates and overcomes these problems, and further provides a relay construction which, at the same time, meets rigid industrial specifications, requiring that each of the switching units of the relay operate at 80% of nominal voltage at its highest expected operating temperature. For example, under these conditions, all `switches are expected to operate or release at or below a given voltage at minimum coil power. For instance, the 80% value of a 24 volt coil; i.e., 19.2 volts, will be reduced, for commercial application to a value of under 15 volts at a operating maximum temperature of 90 C. Heretofore, in order to manufacture each of the switches to meet such severe requirements, rigid tolerances were maintained, leading to considerable scrapping. of switches. The problems will become particularly apparent when one realizes that there is no means possible for :adjustment after the reeds 13 and 14 have once been sealed in the tubes 1S. However, the present invention contemplates the fact that coils vary in ux density at certain areas of the coil configuration, and takes advantageofV this fact in providing :a relay wherein each contact is disposed in optimum operating position relative to the eld intensity of the coil.

In accordance With this discovery, each of the switching units 10 are made in accordance with t-he best known manufacturing techniques, within relatively broad and reasonable tolerances. The switches are `then sorted, selected and placed into groupings according to the number of ampere-turns required to operate the contacts to closed positions and to release the contacts to open position. That is, a standard test coil is provided for sorting purposes (not shown). This test coil consists of 10,000 turns of No. 36 wire and is 1% inches long. Thus, for instance, each of the switching units 10 may be taken from the manufacturing line and placed in the standard coil for measurement of its operate and release characteristics. Thereafter, the switches -10 are sorted into containers for proper selection. The switching units 10, designated by column and rows AW, DW, AZ and DZ of FIG. 2, are disposed in areas of relatively high illux density. lFor instance, a typical 24 v-olt relay may be built to comprise switching units sorted into a range of 94-101 ampere-turns to operate the contacts from nor,- mally-open to closed position, whereas release of the contacts Will fall within a range of 38-43 ampere-turns for the same switch. The intermediately disposed switching units of column-rows AX, AY, DX, DY, BW, CW, BZ and CZ requiring greater amounts of tf1-ux, may be selected from those sorted into an operate ampere-turn range of S6-93 and release ampere-turn range of 32- 37. The more remotely disposed switching lunits 10` of column-rows BX, BY, CX and CY would be chosen to operate at 7885 ampere-turns and to release at 26-31 ampere-turns.

Thus, the relative sensitivity of each of these switches will be disposed in positions of higher ilux density of the coil and the relay will end up with all of its switching units 10 operating and releasing at within an approximate 15 volt range at minimum coil power, and thereby t within the industrial specications in one commingled unit. In addition, another major advantage in providing the present construction lies in the fact that all switching units affected by the coil 12 Will operate substantially in unison. It will be apparent that the disposition of the switching units in `accordance with a preselected operatingV range is of a considerable meritorious contribution when one considers the relative difficulty in `manufacturing the pesent type of switching units and the rigid tolerances that have been required previously.

Another important feature of the present invention resides in the novel biasing magnets and 22 used in the normally-closed switching units C and D of column W of FIG. 2, and in the latehing switching units of A and B of column W, and the paired latching units of columns Y and Z of FIG. 2.

Although it is possible to use other magnets, it has been found to be preferable to provide a ceramic magnet of barium ferrite for biasing the reeds 13 and 14 into closed position or for use as a magnetic latch. The characteristics of this ceramic permanent magnet material is that its retentivity is high, and if subjected to a demagnetizing field, it will substantially regain its original magnetic characteristics when the demagnetizing field disappears. The permeability of the ceramic permanent magnet material is very close to unity. Therefore, it is like air and cannot be saturated. In addition, one very important feature is that its field is directional in nature. The magnet 20 is illustrated in the views of FIGS. 3 and 4, and is further provided with a keeper 21 which insures the directional characteristics in the case of normally-closed or.latched switches of column W of FIG. 2. The magnet 22 is used without a keeper for latching pur- Iposes, when one magnet is intended to affect the operate or release characteristics of paired latching switches, such as those4 of columns Y and Z of FIG. 2. Magnets of the ceramic, barium ferrite type also exhibit a high coercive force, as s-hown by the demagnetization curve 2S of the second quadrant of the B-H hysteresis loop of FIG. 6, as well as a low residual induction. The preferred ceramic magnet is of the non-oriented type, but it is within the province of the present invention to utilize oriented barium ferrite magnets, provided that the field inuencing the magnet is maintained so that the induct-ion B is above the knee of the curve 26 of FIG. 6. The advantage of using the non-oriented material will be apparent from the second quadrant curve of the hysteresis loop, wherein the demagnetization characteristics are clearly shown. The main criterion and good design practice governing the use of the oriented material, such as that exhibiting the curve 26 is that the effect of the demagnetizing Vfield must not act to force the shearing line 27 below the knee ZSof the curve 26.

As stated previously, the curve of FIG.6l shows'the approximate demagnetization characteristic of the preferred material, which 'is non-oriented barium ferrite. This curve dictates that an efficient magnet will have a low magnetic length-to-area ratio. Since t-he characteristic is a straight line, special keepers are not necessary for magnetizing the magnet because the so-called shearing line will always dict-ate operation of the demagnetization curve shown. The bias strength of the magnet may be varied by magnetizing only that length L1, as shown in FIG. 3 by means of the magnetizing fix-ture illustrated in FIG. 5. Thus, standard size magnets may bev used and may be substituted in a fixed geometry to obtain varying operate and release characteristics. In a ceramic magnet of the present type, the field is very directional and substantially normal to the longitudinal axis of the magnet 20. Therefore, certain area sections of the magnet, such as those -defined by the areas Llw and Lzw, may beV magnetized independently of one another, as indicated in FIG. 3. The area Llw has its north pole at the upper surface with relation to FIG. 4, and the poles of t-he area L2w is magnetized with its south pole at the upper'surface and the north pole adjacent the keeper 21. Another favorable characteristic of this ceramic permanentmagnet material is that its retentivity -is high, and if subjected to a demagnetizing field, it will regain substantially its original magnetic characteristics when the demagnetizing field disappears. The coercive force of the preferred ceramic magnet is high as indicated by the demagnetiza- 1 tion curve 25, and therefore, the magnet will be effective in the short lengths L1 vand L2. Thus, the coercive force Will be high even with low length-to-area ratios.

Accordingly, the present invention further contemplates a method and apparatus for magnetizing the magnets 20 in the discrete sections defined by the areas Llw and L2w. The fixture (see FIG. 5) used in magnetizing the magnets 20 or 22, in general, comprises two armatures or cores 30 and 31, which are movable laterally relative to one another by means of a simple adjustment means, such as individual worm screws 32 and 33 terminating in knobs 34. The details of the worm screws and the support for the armatures should be obvious to those skilled in the art, and are not herein shown in detail. Each of the armatures 30 and 31 are provided with separate coils 35 and 35, respectively. Thus, D.C. current of, for instance, a value sufficient to produce a magnetizing eld of 10,000 gau-ss in the air gaps, is applied to the armature through its respective coils 35 or 36 and will provide a fiuX path, as shown at 37, through a block of iron or pole piece 38 and a supporting block of iron or pole piece 39. Armatures 30 and 31 are movable relative to the stationary blocks 38 and 39. A brass, or other non-magnetic, plate 40 is disposed at the upper surface of the base magnetic block 39 and is recessed to receive the magnets 210 or 22.

As shown in FIG. 5, the coils 35 and 36 are wound in such manner as to provide a fiux path 3'7 as to magnetize discrete areas Llw and Lgw with the north pole of area Llw being at the top surface of the magnet 20 viewed at the left of FIG. 5, and the south pole of the top surface of the area L2w, as viewed at the right of FIG. 5. In this manner, the areas Llw and L2w may be enlarged or decreased as desired without requiring a change in magnet size or shaving of surfaces to provide variati-ons in crosssection or other means of varying the flux of the magnet. These areas are merely changed by moving the armatures 30 or 31 inwardly or outwardly relative to one another by turning the respective knobs 34 and their respective worm screws 32 and 33.

The magnet 20 an-d its keeper 21 are removed and placed adjacent a respective switching unit 10 to provide the desired biasing effect. The magnet is magnetized so as to operate the reed contacts 13 and 14 -for normallyclosed or latched position as shown at positions CW, DW, AZ, BZ, CZ and DZ of FIG. 2, in order that they will operate within a specified ampere-turn range. Obviously, the degree of magnetization for latching contacts of positions AW, BW and those lof columns Y and Z will be less than that lrequired for normally-closed contacts CW and DW. The -field is very directional and will affect only the particular reeds in question, and will not affect an adjacent normally-open contact, such as those of column X of FIG. 2 when the keeper 21 is used. Nor will the switches of column X be affected by the biasing action of the magnets 22 for the latching pairs of columns Y and Z.

Thus, current in the coil 12 will provide a fiux path in opposition to the magnets 20, so as to open the normally-closed contacts of the columns W and Z and to close the normally-open contacts of the columns X and Y. In the case of the latching contacts of columns Y and Z, the respective contacts will remain in the position other than the normal position upon cessation of the current supplied vto the coil 12. Obviously, the present invention permits rearrangement of the switching units as desired, just as long as the magnets affecting all contacts of a particular column are of like structure.

As far as the magnetization of the magnet is concerned, it will be appreciated that individual magnets 2t) or 22 must at least match the ampere-turns of the coil necessary to operate a particular switch 1f) from its normally-closed position, or to hold the contacts of a particular switch in latched position when current is interrupted in the coil.

Referring to the diagram of FIG. 7, it will be observed that a switch (for purposes of illustration, the switch having characteristics wherein, it will open within a range or band of 78-102 ampere-turns and will close within a band of 26-42 ampere-turns) has certain operate and release characteristics which are affected by the combined flux of the biasing magnet and the coil. The switch exhibits four sensitivity points of operation, as indicated at the zero ordinate, where no magnet is used, as in the case of a switch with a normally-open contact. The band defined by +78 and +102 ampere-turns, for example, defines a range which insures the operation of the contacts to contact-closed position, whereas the band defined by +26 and +42 ampere-turns indicates a range which insures that the contacts will be open. That is, if one follows the zero ordinate vertically from the zero abscissa, it will be observed that the normally-open contacts of the present preselected assortment will begin to close as the coil flux is increased in a positive direction to the value of +78 ampere-turns, and all will be closed when current is supplied in an amount equal to +102 ampere-turns. As the positive current is decreased, the contacts will begin to release at +42 ampere-turns and will all be open .at +26 ampere-turns.

A mirror image of the action takes place in the negative area below the zero abscissa, and as negative current Vis supplied to lthe coil, the normally-open coils will remain open until a coil iiux value of -78 ampere-turns is reached and will all be closed when a value of -102 arnpere-turns has been supplied thereto. Decrease of negative current supplied to the coil will permit the contacts 'to open between -42 and +26 ampere-turns.

In the case of providing a biasing magnet for holding contacts in normally-closed position, such as those indicated at CW and DW of FIG. 2, it will be apparent that 'the biasing magnet must be magnetized `in areas Llw and L2w with a flux equivalent to 102 ampere-.turns or in excess of this amount when positive current is supplied. It will be necessary to provide the coil with negative current beforethe contacts will open.

In'the matter of providing a biasing magnet for latching type contacts, such as those indicated at AW and BW and the paired switches AY, BY, CY, DY, AX, BX, CX, and DX of FIG. 2, the magnets and 22, respectively, are magnetized in areas Llw and Lzw to provide a flux equivalent to ampere-turns that fall within the operate and release range, such as +78 and +102 and +26 and +42, respectively, in the case of the preselected contact assortment under present discussion. Similar selection would be true for other switch operating characteristics. The present biasing magnet will then act to shift the sensitivity values to the right of the diagram of FIG. 7, and in the present case to intersect with the vertical line indicated yby the dot-dash line drawn at an arbitrarily selected magnet flux value of 57 ampere-turns. This value'is preferably chosen to lie intermediate the operate and release bands. Thus, it will be observed that the magnet will shift the coil flux necessary to open the contacts from the 78-102 ampere turns positive current band t-o a lesser value of approximately 22-46- positive current ampere-turn band. This shift is due to the fact that the permanent magnet acts in combination with the coil to supply the total flux necessary to operate the icontacts.

1t will be further observed that the contact open, or release band has been shifted by the magnet to nega- 'tive values of approximately -12 to +28 ampere-turns.

lThe negative contact open release band is also shifted,

as is the negative contact closed or operate band, but to higher negative values of approximately -82 to -98 ampere-turns and -135 to -159 4ampere-turns, respectively. Referring to the Vertical dot-dash line at 57 arnpere-turns of magnet flux, it will be apparent that as positive current vis 'supplied to the coil, the contacts will close between avalueof approximately +22 and +46 ampere-turns, and remain closed, or latched, even after the current is interrupted. It will take a negative curl8 rent to release the contacts and of approximately -12 to +28 ampere-turns. It is of interest to note that the contacts will then remain open until a value of approximately ampere-turns is reached. Here, there will be no latching effect upon interruption of current, as the contacts will again open as the negative current is released to the Iband of approximately 82-98 ampere-turns. However, the magnet may be magnetized in such manner as to latch within the negative coil flux operate band by simply reversing the magnet with respect to the reeds 13,`

14 or to reverse the input to the coil 12.

It will be apparent that since the preferred ceramic magnets of the present invention lend themselves to magnetization of discrete areas .and are very directional in nature, that it is within the scope of this invention to supply magnets (not shown) which are of equivalent size as the areas Llw and Lzw, but which are independent from one another and separately fastened to opposite ends of a keeper (such as keeper 21). The keeper would be of ferromagnetic material for use with switches, such as those of columns Y and Z of FIG. 2, a non-magnetic supporting bar would be used with the ceramic magnetic slugs being fastened by cement to other means to extend from opposite ends thereof (not shown).

Another importantaspect of the present invention results from the use of ferrite biasing magnets, which perymit automatic temperature compensation of the biased contacts. Since the coil ux is produced lby the coil ampere-turns, and since an increase in temperature causes the coil resistance to increase, the coil iiux in terms of ampere-turns will -be less for a given coil voltage at a relatively higher temperature. This was the reason for specifying l5 volts as a minimum col operating voltage, corresponding to a measurement on a cold coil for the operating temperature increases due to increase in coil Thus, the coil operating voltage will not` resistance. vary appreciably with changes in temperature. This effectis only apparent in the biased contacts of the switching units.

While this invention has been herein described by reference to specific embodiments of the same, it is intended that the protection of Letters Patent to be afforded hereby be not unnecessarily limited by such description, the intention being that such protection extend to the full limit of the inventive advance disclosed herein as defined lby the claims hereto appended.

I claim:

1. Inv the manufacture of a relay comprising a plurality of sealed switching units having individual operating characteristics and a common energizing coil defining a window and which coil when energized produces a variable magnetic eld within the window, said field varying from a maximum at the periphery of the window to a minimum at the center point of the window; the irnproved manufacturing procedure of individually subjecting a plurality of switching uni-ts of unknown operating characteristics to the magnetizing field of a standard coil of preselected dimension and coil flux, sorting said switching units into groups in accordance with the amount of coil iiux required to operate the units by said standard coil, and positioning said switching units within the window, a number of said switching units being positioned adjacent to the periphery of the window and at least one of said switching units being positioned remote from the Y the variable magnetic eld of said common energizing coil corresponding with the amount of iiux needed to operate the respective sorted switching unit.

2. In the manufacture of a relay comprising a plurality of sealed switching units having individual operating characteristics and a common energizing coil dening a window and which coil when energized produces a variable magnetic ield within the window, said iield varying from a maximum at the periphery of the window to a minimum at the center point of the window and wherein it is desired to operate said units substantially in unison or in a desired sequence; the improved manufacturing rocedure of individually subjecting a. plurality of switching units of unknown operating characteristics to the magnetizing field of a standard coil of preselected dimension and coil ilux, sorting said switching units into groups in accordance with the amount of coil flux required to operate the units by said standard coil, and positioning said switching units within the window, a number of said switching units 'being positioned adjacent to the periphery of the window at least one of said switching units being positioned remote from the periphery of the window and intermediate switching units positioned adjacent to the periphery of the window, each switching unit being positioned in a predetermined area of the variable magnetic eld of said common energizing coil corresponding with the amount of iiux needed to operate the respective sorted switching unit in substantially simultaneous operation with the others of said units or in a desired sequence of operation therewith.

3. in the manufacture of a relay comprising a plurality of sealed switching units having individual operating characteristics and a common energizing coil of rectangular c-ontiguration and defining a window therein for receiving said switching'units, said coil producing a magnetic iield Within the window through said switching units when energized, said iield varying from a maximum at the periphery or the window to a minimum at the center point of the window; the improved manufacturing procedure of individually subjecting a plurality of switching units of unknown operating characteristics to the magnetizing field of a standard coil of preselected dimension and coil flux, sorting said switching units into groups in accordance with the amount of coil ux required to operate the units by said standard coil, and positioning said switching units in said coil window, a number of said switching units being positioned adjacent to the periphery of the window and at least one of said switching units being positioned remote from the periphery of the window and intermediate switching units positioned adjacent the periphery of the window, each switching unit positioned in a predetermined area of the variable magnetic field of said common energizing coil corresponding with the amount of flux needed to operate the respective sorted switching unit.

References Cited by the Examiner UNITED STATES PATENTS 2,796,658 6/1957 Aller 29--148-4 2,924,333 2/1960 Kulick 209-75 3,015,707 l/l962 Perrault 20G-87 3,020,369 2/1962 Jacobson 20G-104 3,114,019 12/1963 oda 200-87 JOHN F. CAMPBELL, Primary Examiner.

I. M. ROMANCHIK, Assistant Examiner. 

1. IN THE MANUFACTURE OF A RELAY COMPRISING A PLURALITY OF SEALED SWITCHING UNITS HAVING INDIVIDUAL OPERATING CHARACTERISTICS AND A COMMON ENERGIZING COIL DEFINING A WINDOW AND WHICH COIL WHEN ENERGIZED PRODUCES A VARIABLE MAGNETIC FIELD WITHIN THE WINDOW, SAID FIELD VARYING FROM A MAXIMUM AT THE PERIPHERY OF THE WINDOW TO A MINIMUM AT THE CENTER POINT OF THE WINDOW; THE IMPROVED MANUFACTURING PROCEDURE OF INDIVIDUALLY SUBJECTING A PLURALITY OF SWITCHING UNITS OF UNKNOWN OPERATING CHARACTERISTICS TO THE MAGNETIZING FIELD OF A STANDARD COIL OF PRESELECTED DIMENSION AND COIL FLUX, SORTING SAID SWITCHING UNITS INTO GROUPS IN ACCORDANCE WITH THE AMOUNT OF COIL FLUX REQUIRED TO OPERATE THE UNITS BY SAID STANDARD 